Automated door assembly, press, and adhesive therefor

ABSTRACT

A system and method for making a door having first and second door skins and an internal frame. The top and bottom surfaces of the frame are coated with an adhesive and the frame is placed on a first door skin. The second door skin is then placed on the opposite surface of the frame. The assembled components are then pressed to bond the first and second door skins to the frame with a pressed having platens. Movable shims may be used to vary the pressed force and pressing area.

PRIORITY

This application is a divisional of U.S. application Ser. No. 14/341,193filed Jul. 25, 2014, which is patented as U.S. Pat. No. 9,511,573 andalso claims the benefit of priority of Provisional Application No.61/858,334 filed Jul. 25, 2013, the complete disclosures of which areincorporated herein by reference and to which priority is claimed.

FIELD OF THE INVENTION

The present invention is directed to presses for door assemblies,automated door assembly processes and stations, and related methods.

BACKGROUND

Doors are typically made from two molded or flush door skins attached toopposite sides a central door frame. The door facings are often moldedfrom a wood fiber and resin compound, although fiberglass resin formedpolymer door facings are known. The door frame typically includes stilesand rails made of wood located around the perimeter of the door. Theinterior of the door may optionally include a core.

Manual assembly of doors is relatively labor intensive, expensive, andsubject to quality variations. During manual assembly, a door facing isplaced on a production table with its intended exterior surface facedown. Adhesive is then applied to the stiles and rails of a frame. Theadhesively coated frame parts are then placed on the door facing on thetable. Adhesive applied to a second side of the stiles and rails facesupwardly and a second door facing is placed with its exterior surfaceface upon the second side of the frame. The resulting assembled door isstacked at a holding station so that additional doors may be assembled.The assembled doors should be handled carefully, given that thecomponents of the door can easily shift during transportation.

Each successive door assembly is stacked on top of the previous doorassembly until a predetermined quantity of door assemblies has beenstacked. The stack of door assemblies is then transported to and loadedin a press. The press applies pressure to the entire stack for a periodof time sufficient to allow the adhesive to bond the door facings to theframe. Conventional adhesives, such as polyvinyl acetate, may takeapproximately thirty minutes or more in-press before the door reaches“green” strength. The door achieves green strength when the adhesive hasreached sufficient bonding strength to hold the door components togetherfor further handling.

Once an acceptable green strength is achieved, the doors may be removedfrom the press and moved to an in-process inventory until the adhesivereaches maximum cure strength. Depending on the adhesive used, the doorsmay need to remain in inventory for a relatively long period of time,for example two hours or more, or even as long as twenty-four hours,before the adhesive reaches maximum bonding strength.

After reaching maximum cure strength the doors are then moved to a finalprocessing station. Final processing includes edge trimming the doors tocustomer specification and optional coating and/or painting of doorskins and exposed edges of the stiles and rails around each doorperimeter. Using this process, manufacturing time for a door may betwenty-four hours or more, from the time production is initiated to theresulting finished door is complete.

SUMMARY

In accordance with an embodiment, a door-making system includes at leastone adhesive coating station, at least one assembly station, and atleast one pressing station. The coating station applies adhesive to atleast one of a door frame, a first door skin, and a second door skin.The assembly station joins the first and second door skins to oppositesurfaces of the frame. The pressing station includes a first press and asecond press for alternately receiving the assembled doors.

In accordance with a further embodiment, a door pressing stationincludes at least one press having an upper die and a lower die. Theupper die has an upper convex surface and the lower die has a lowerconvex surface. The upper and lower convex surfaces face one another todefine a mold cavity. In an alternative embodiment, the upper and lowerconvex surfaces are formed by inserts or shims which form steppedsurface(s) having a central area that is raised above the perimeterareas. One or more of the shims may be hydraulically driven to raiseabove the surface of the perimeter areas.

In accordance with a further embodiment, a method of making a doorincludes adhesively bonding a first door skin and a second door skin toopposite sides of a frame to assembly doors as part of a productionprocess. The assembled doors are alternately received in a first pressand a second press.

In accordance with another embodiment, a method of pressing an assembleddoor includes loading a door assembly into a press having an upper diewith an upper convex portion and a lower die with a lower convexportion. The upper and lower convex surfaces face one another to pressthe door assembly.

Another embodiment provides a door press for pressing door assemblies ofdifferent sizes. The door press includes a first die having a firstfixed surface, a plurality of first movable shims having first movableshim surfaces, and a second die having a second fixed surface facing andrelatively movable towards and away from the first fixed surface. Thefirst movable shims are movably connected to the first die to movebetween at least a raised position in which the first movable shimsurfaces are substantially flush with the first fixed surface and alowered position in which the first movable shim surfaces are recessedinto the first die relative to the first fixed surface.

Still another embodiment provides a door-making system including atleast one adhesive coating station for applying adhesive to at least oneof a door frame having opposite first and second surfaces, a first doorskin, and a second door skin, at least one assembly station forrespectively joining the first and second door skins to the oppositefirst and second surfaces of the door frame to form an assembled door, adoor press, and at least one material handling device for transportingthe assembled doors to and from the door press. The door press includesa first die having a first fixed surface, a plurality of first movableshims having first movable shim surfaces, and a second die having asecond fixed surface facing and relatively movable towards and away fromthe first fixed surface. The first movable shims are movably connectedto the first die to move between at least a raised position in which thefirst movable shim surfaces are substantially flush with the first fixedsurface and a lowered position in which the first movable shim surfacesare recessed into the first die relative to the first fixed surface.

Yet another embodiment provides a method of pressing a door assemblywith a press that includes a first die having a first fixed surface, aplurality of first movable shims having first movable shim surfaces, anda second die having a second fixed surface facing and relatively movabletowards and away from the first fixed surface. The first movable shimsare movably connected to the first die to move between at least a raisedposition in which the first movable shim surfaces are substantiallyflush with the first fixed surface and a lowered position in which thefirst movable shim surfaces are recessed into the first die relative tothe first fixed surface. According to the method, the first movableshims are selectively adjusted into the raised position or the lowerposition so that a combined area of the first fixed surface and thefirst movable shim surfaces of the first movable shims in the raisedposition corresponds to a surface area of a face of the door assembly.The door assembly is then pressed in the press.

Other embodiments, including apparatus, systems, methods, and the likewhich constitute part of the invention, will become more apparent uponreading the following detailed description of the exemplary embodimentsand viewing the drawings. It is to be understood that both the foregoinggeneral description and the following detailed description are exemplaryand explanatory only and therefore not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary automated door productionline.

FIG. 2 is a sectional, plan view of a defective door.

FIG. 3A is a plan view of an exemplary door facing having adhesiveapplied thereto.

FIG. 3B is a plan view of another exemplary door facing having adhesiveapplied thereto.

FIG. 4 is a plan, schematic view of an exemplary double press.

FIGS. 5A-5C are sectional, schematic views of an exemplary pressingprocess for a door assembly.

FIG. 6 is a sectional, schematic view of an exemplary press and doorassembly.

FIG. 7A is a plan view of an exemplary post-press door assembly.

FIG. 7B is a sectional, plan view of the door assembly of FIG. 7A takenalong line 7B-7B.

FIG. 7C is a sectional, plan view of the door assembly of FIG. 7A takenalong line 7C-7C.

FIG. 8 is a sectional, schematic view of a door assembly in an exemplarydoor press utilizing spacers.

FIG. 9 is a sectional, schematic view of a door assembly in an exemplarydoor press utilizing attached plates.

FIG. 10 is a sectional, schematic view of a door assembly in anexemplary door press utilizing membranes.

FIG. 11 is a sectional, schematic view of a door assembly in anexemplary door press utilizing expandable membranes.

FIG. 12 is a plan view of an alternative embodiment of the upper andlower platens having a stepped central portion that is raised above theperimeter region of the platen.

FIG. 13 is a back side view of the platen shown in FIG. 12 showingvarious hydraulic ports.

FIGS. 14A-14C, the platen 70, 74 is illustrated with the peripheralshims 190, 192 in various positions with respect to central shim 180.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S) AND EXEMPLARY METHOD(S)

Reference will now be made in detail to exemplary embodiments andmethods as illustrated in the accompanying drawings, in which likereference characters designate like or corresponding parts throughoutthe drawings. It should be noted, however, that the invention in itsbroader aspects is not limited to the specific details, representativedevices and methods, and illustrative examples shown and described inconnection with the exemplary embodiments and methods.

FIG. 1 depicts an automated door production line 1. In an exemplaryembodiment, the door production line 1 is a synchronous system designedto operate at a specific rate of movement, for example, one doorproduced per unit of time. In order to avoid bottlenecks, each step inthe process, including transportation, occurs at the specific rate ofmovement. Therefore, it is important to provide suitable press time andproper adhesive application to sufficiently bond the components of thedoor together. Improper bonding can lead to quality issues.

FIG. 2 shows a door D1 having such quality issues. Improper bonding timecan cause the separation or delamination of the door skins S1, S2 fromthe core element C. Delamination is especially persistent in door skinsS1, S2 having a number of molded panels. For example, molded six paneldoor skins S1, S2 bonded to a core C with a hot melt adhesive usingconventional processes may experience delamination across the width ofthe door D1. The delamination between skins S1, S2 and the core C is anindication of internal polyurethane (PUR) adhesive bond failure whichmay be caused by tension stresses or spring-back of the bowed skins andcompressed core areas in the ovolos, or molded panel design areas, ofthe molded skins S1, S2. In these cases, the initial green or setstrength of various PUR formulations along with typical PUR roll coatingand door pressing approaches may not overcome the stresses leading todelamination. Pre-cured back surfaces of the door skins S1, S2 may alsoprevent effective PUR wetting when the adhesive is applied only to theframe. To overcome these deficiencies various improvements in theprocess have been made.

FIG. 1 shows the production line 1 having an exemplary series ofstations for assembling a door. Various material handling and movementdevices and methods may be used to transport components of the doorassembly, and are simply designated by the arrows in the individualstations and between stations. Material handling and movement devicesmay include, for example, conveyors, gantry, manipulators, grippers,automated guided vehicles, and automated storage/retrieval systems. Thecomponents and stations of the production line may be operated by anoperator's control, automatically utilizing various sensors includingoptical, magnetic, and radio sensors, or any combinations of manual andautomatic operation. Though specific examples of material handling andmovement may be provided in the exemplary description of certainstations, these may be modified as would be understood by one ofordinary skill in the art upon viewing this disclosure.

As shown in FIG. 1, a stile assembly station 10 includes a lock blockindexing device 12 and a stile indexing device 14. In an exemplaryembodiment the stile indexing device 14 removes stiles 2 from a firststile conveyor 16 and a second stile conveyor 18. A single stileconveyor, a set of first and second stile conveyors 16, 18, or more thantwo stile conveyors may be utilized depending on the throughput rate.More stile conveyors or sets of stile conveyors allow an increase in thethroughput rate of the production line 1. When a pair of stiles 2 havebeen removed from the top level conveyor of the first and second sets ofstile conveyors 16, 18, a new pair of stiles 2 is delivered to the toplevel conveyor to replace them. Because conveying the stiles 2 to theappropriate position to be picked up by the stile indexing device 14 maytake longer than the movement rate of the system, the stile indexingdevice 14 alternatively may take the next pair of stiles 2 from the nextlevel of conveyors.

As the stiles 2 are being retrieved by the stile indexing device 14,lock blocks 4 are removed by the lock block indexing device 12 and movedalong a conveyor 20 or other suitable material transportation device.The lock blocks 4 may be removed by the lock block indexing device 12 ina manner similar to the stiles 2, or the lock blocks 4 may be removedfrom a pallet containing multiple lock blocks 4. Both the stiles 2 andthe lock blocks 4 are moved to a lock block attachment station 22. Atthe lock block attachment station 22, the lock blocks 4 are connected tothe stiles 2. The lock blocks 4 may be attached to the stiles 2 viaadhesive, for example a hot melt adhesive, a mechanical fastener, or acombination thereof. While FIG. 1 depicts a lock block 4 being attachedto each stile 2, optionally only a single lock block 4 may be attached.The movement and handling of all the components in stations 10 and 22may be handled manually or automatically by robotic systems such as pickand place robotic arms, robotic indexers, and the like.

Rail assembly station 24 includes a rail indexing device 26 whichselects a pair of rails 6 a, 6 b from a rail conveyor system 28. In anexemplary embodiment the rail conveyor system 28 includes a top railconveyor 30 and a bottom rail conveyor 32, though a single railconveyor, or more than two rail conveyors may alternatively be used asdiscussed above in connection with the first and second stile conveyors16, 18. As shown in FIG. 1, a single top rail 6 a may be selected fromthe top rail conveyor 30 and a single bottom rail 6 b is selected fromthe bottom rail conveyor 32. In various exemplary embodiments, a doorhaving more than one top rail 6 a, such as a double top rail (notshown), more than one bottom rail 6 b, such as a double bottom rail (notshown), or both a double bottom rail and double top rail, and/or one ormore intermediate rails (not shown) may be desired. Therefore, the railindexing device 26 may be capable of variably selecting a single rail 6a, 6 b or multiple rails from the top rail conveyors 30, the bottom railconveyors 32, and optionally intermediate rail conveyors (not shown). Ifmore than a single top and/or bottom rail 6 a, 6 b is selected, the tworails 6 a, 6 b are attached, for example, by fasteners or an adhesivesuch as a hot melt adhesive to form the double rail.

After being selected, the rails 6 a, 6 b are moved to a core attachmentstation 34. At the core attachment station 34, a core C is connected tothe top rail 6 a and the bottom rail 6 b, for example, by a hot meltadhesive. The core C may be brought to the core attachment station 34 bya conveyor or indexing device (not shown) similar to those shown anddescribed with respect to the lock blocks 4, stiles 2, or rails 6 a, 6b. The core C may be an expandable core or a solid core, such as,fiberboard, or any suitable substance depending on the door. In anexemplary embodiment, the core C is an expandable corrugated cardboardcore or honeycomb paper core. The production line 1 may be set up andutilized so that the core C is variable and optional so that differentcores C may be selectively attached to the rails or omitted from theassembled frame. Optionally the core may be formed in situ.

The attached lock block 4 and stile 2 assembly and the attached rail 6a, 6 b and optional core C are then transferred to the frame assemblystation 36. Robotic handling devices such as a clamp and gantry systemmay be used to deliver the frame components to the frame assemblystation 36. When an expandable core C is used, the rails 6 a, 6 b may bedrawn apart to expand the core C. The rails 6 a, 6 b and stiles 2 arethen attached together to form an assembled frame F. The rails 6 a, 6 band stiles 2 may be attached with mechanical fasteners, an adhesive, forexample, a hot melt adhesive, or any combination of fasteners andadhesive. In various exemplary embodiments, different combinations ofthe lock blocks 4, stiles 2, rails 6 a, 6 b, and core C may bepreassembled before reaching the production line. It should be notedthat the term frame F used throughout the rest of this descriptionincludes the assembled stiles 2, rails 6 a, 6 b, optional lock block(s)4, and optional core C.

When the frame F is assembled, either through the assembly system andprocess described above, preassembly, or a combination thereof, theframe F is moved to a frame adhesive station 38. In an exemplaryembodiment, the frame adhesive station 38 is capable of applying anadhesive to both sides of the frame F. Adhesive application may beaccomplished by passing the frame F through a double roll coater of theframe adhesive station 38. In an exemplary embodiment, the roll coaterapplies adhesive to the frame F in an amount between about 6 and about35 g/sft (grams per square foot) as measured on a surface of the stiles2 or rails 6 a, 6 b. In various exemplary embodiments, the amount ofadhesive is between about 15 and about 26 g/sft. This amount of adhesivemay help prevent quality issues, such as pillowing discussed above.After the adhesive is applied, the frame F is transferred to a door skinassembly station 40. Robotic handling devices such as a clamp and gantrysystem 39 may be used to deliver the frame from the frame adhesivestation 38 to the door skin assembly station 40.

The door skin assembly station 40 includes a first skin feeder 42 and asecond skin feeder 44. The first skin feeder 42 may include a door skinpallet 46 a or multiple pallets of door skins. Similarly, the secondskin feeder 44 may include a door skin pallet 46 b or multiple palletsof door skins S1, S2. In an exemplary embodiment, the first skin feeder42 provides a bottom door skin S2 and the second skin feeder 44 providesa top door skin S1. The top and bottom door skins S1, S2 may beidentical or different depending on the production requirements. The topand bottom door skins S1, S2 may be any variety of door skins includingwood composite door skins, solid wood door skins, polymer door skins,sheet molding compound door skins, molded door skins, and flush doorskins. Though two skin feeders 42, 44 are shown, a single skin feedermay be utilized which provides both the top and bottom door skins S1,S2.

Door skins S1, S2 may be unloaded from the pallets 46 a, 46 b and placedon a conveyor (not shown) either manually or through a robotic handlingdevice such as a vacuum gantry. If the door skins S1, S2 are removedfrom the pallets 46 a, 46 b manually, the operator moving the door skinsS1, S2 may perform a visual quality inspection. If a door skin S1, S2 isfound to be unsatisfactory, the operator may place it on a disposalconveyor. If the door skin S1, S2 is found to be acceptable, theoperator may place it on a production conveyor. Alternatively, the doorskin S1, S2 may be removed from the pallets 46 a, 46 b with an automateddevice and a camera or set of cameras may be set up so that a remoteoperator can perform visual inspection. The operator is then able todetermine if the door skins S1, S2 are acceptable and signal the robotichandling system to place the door skins S1, S2 on either the productionconveyor or the disposal conveyor. In various exemplary embodiments, theinspection may be performed automatically by tactile inspection devices,such as touch probes, or non-tactile inspection devices, such as laseror optical sensors. For example, a camera may optically capture theimage of a door skin S1, S2. The image may then be processed andmeasured by a microprocessor. If the door skin S1, S2 is acceptable, themicroprocessor can signal the robotic handling device to place the doorskin S1, S2 on the production conveyor. If the door skin S1, S2 is notaccepted, the microprocessor signals the robotic handling device toplace the door skin S1, S2 on the disposal conveyor.

The first and second pallets 46 a, 46 b may have door skins S1, S2facing the same direction. For example, the door skins S1, S2 in pallets46 a, 46 b may have an intended exterior surface (depicted in white)facing up. Depending on the parameters of the production line 1, thedoor skins S1, S2 from one or both pallets 46 a, 46 b may need to beflipped so that their intended interiorly disposed surface (shaded) isfacing down. In the exemplary embodiment shown in FIG. 1, after a doorskin S2 is removed from the first skin feeder 42, it is transferred to afirst flipping station 48. The first flipping station may utilize anyautomated flipping apparatus, for example a star conveyor. Optionally,before the bottom door skin S2 is connected to the frame, a firstadhesive applicator 50 applies a layer of adhesive to the interiorsurface of the door skin S2. The first adhesive applicator 50 may be afirst spray coater with one or more spray heads.

In various exemplary embodiments, the first adhesive applicator 50 iscapable of applying adhesive to the door skin S2 in beads or lines. Asbest shown in FIGS. 3A and 3B, the device may be a nozzle or jet capableof applying under pressure a liquid form of an adhesive, for example ahot melt adhesive such as PUR or ethylene vinyl acetate (EVA), to a doorskin S2. The adhesive may be applied in individual lines, such as thewavy lines A1 as shown in FIG. 3A. The adhesive lines A1 are verticallyorientated and placed just outside of and down the middle of the panelsP. The type of adhesive application shown in FIG. 3A is one way toprevent delamination of the door skin S2 from the core C.

In the exemplary embodiment shown in FIG. 3B, a bead A2 of adhesive isapplied to each panel P. Applying the adhesive to the door skin S2 inthis way creates a spot-weld-type gluing effect when the door skin S2 ispressed to the core C, further bonding the door skin S2 and the core Creducing the chance of delamination. Various other glue patterns, suchas a web pattern or a checkered pattern, or combinations of gluepatterns may be utilized depending on the configuration and design ofthe door skins S1, S2. In various exemplary embodiments, the firstadhesive applicator 50 is capable of applying different adhesives in avariety of patterns and locations so that different door types may bemade on a single production line 1.

After the optional adhesive application, the bottom door skin S2 ismoved to the first door assembly station 52. The bottom door skin S2 maybe moved by a robotic handling device such as a vacuum gantry, conveyor,or combination thereof. The adhesively coated frame F is transported tothe first door assembly station 52 and placed onto the bottom door skinS2. Various stops, limits, tactile sensors, and non-tactile sensors maybe used to align and position the bottom door skin S2 and the frame F.

Similar to the bottom door skin S2, the top door skin S1 is transferredfrom the second skin feeder 44. The top door skin S1 may have anoptional adhesive coating applied by a second adhesive applicator 54.The second adhesive applicator 54 may include all the features andcapabilities discussed above with respect to the first adhesiveapplicator 50. Accordingly, the second adhesive applicator 54 may beidentical to or different from the first adhesive applicator 50.

As discussed above, the second pallet of skins 46 b has the exteriorsurface of the top door skins S1 facing up. Therefore, to apply adhesiveto the interior surface, the top door skin S1 is flipped at a secondflipping station 56. Because the top door skin S1 is placed onto the topsurface of the frame F, it must be flipped again at a third flippingstation 58 after the adhesive is applied. Various exemplary embodimentsmay omit application of adhesive to the top door skin S1 and thereforethe second and third flipping stations 56, 58 may be bypassed oromitted. Additionally, the second adhesive applicator 54 may be capableof applying adhesive from underneath the top door skin S1 so that thesecond and third flipping stations 56, 58 may be omitted. Alternatively,the door skins S1, S2 in pallets 46 a, 46 b may be providedinterior-side up so as to avoid the use of the flipping stations 48, 56.

After the optional adhesive application, the top door skin S1 is movedto a second door assembly station 60. At the second door assemblystation 60 the top door skin S1 is placed onto the frame F opposite thebottom door skin S2 so that the interior surface of the top door skin S1faces down towards the frame F. Various stops, limits, tactile sensors,and non-tactile sensors may be used to align and position the door skinS1 and the frame F.

In various exemplary embodiments, the door skin assembly station 40includes a device or devices for applying a liquid, for example water,to the inner surface of the door skins S1, S2 before they are attachedto the frame. A spray head or other suitable device can apply water, forexample in a misting spray, to the inner surface of the door skins S1,S2. The liquid may be applied by the first and second adhesiveapplicators 50, 54 in connection with an adhesive or variably without anadhesive. Alternatively, the liquid may be applied prior to, orsubsequent the optional adhesive application. The application of waterhelps prevent warping and may improve skin wetting and increase the bondquality between resin that may be present in the door skins S1, S2 andthe frame and the core C. The amount of water applied is enough todampen the inner surface of the door skins S1, S2, though more water maybe applied so that the moisture permeates at least partially into thedoor skins S1, S2. Other surface treatments may also be applied to thesurface in addition to water or alternatively to water in order toincrease bond quality.

After the top door skin S1 is connected to the frame F, the assembleddoor is transferred to a pressing station 61 where the door is pressedto more fixedly bond the door skins S1, S2 to the frame F and core C. Asdiscussed above, because the production line 1 is automated, each stepis performed at the set rate of movement to avoid bottlenecks. Forexample, the amount of time for the lock block attachment station 22 toattach the lock blocks 4 to the stiles 2 is equal to rate of movement,the time for the frame F to be transferred to the first door assemblystation 52 equals the rate of movement, and the time in betweencompleted doors coming off the production line 1 is equal to the rate ofmovement. In various exemplary embodiments, the rate of movement of thepresently described system is about 7 seconds to about 15 seconds, forexample about every 8 seconds, though the time may vary depending onseveral factors such as the adhesive selected, as would be understood byone of ordinary skill in the art upon viewing this disclosure. The rateof movement may not be long enough, however, for sufficient bondstrength to form between the door skins S1, S2 and the frame F and coreC.

To allow for a pressing time that exceeds the rate of movement, a doublepress 62 is used. The double press includes an upper press 62 a and alower press 62 b. As shown in FIG. 1, a first assembled door istransferred onto a loading table 63 a. The loading table 63 a may be atwo-position table and may include a conveyor device, such as poweredrollers, to move the assembled doors on and off the loading table 63 a.The loading table 63 a places an assembled door into one of the top andbottom presses 62 a, 62 b, for example the bottom press 62 b. After theproduction line 1 moves again, a second assembled door is loaded ontothe loading table 63 a and the loading table 63 a is raised to place thesecond assembled door into the upper press 62 a. After the productionline 1 moves again, the first assembled door is removed from the lowerpress 62 b and transferred to a discharging table 63 b. The dischargingtable 63 b may be a two-position table and may include a conveyordevice, such as powered rollers, to move the assembled doors on to andoff of the discharging table 63 b. As the first door is transferred fromthe lower press 62 b, the loading table 63 a places a third assembleddoor in the lower press 62 b to replace the first assembled door. Usingthe double press 62, the pressing of assembled doors is alternatedbetween the upper and lower presses 62 a, 62 b. An assembled door cantherefore undergo a pressing operation, which may include the openingand closing the dies of the upper and lower presses 62 a, 62 b, forapproximately twice as long as the rate of movement. The extra presstime allows a greater bond to be created between the door skins S1, S2,and the frame F and the core C.

In various exemplary embodiments, the press imparts approximately 100psi to the door skins S1, S2 adjacent the stile and rail sections. Thepressure along the remaining areas of the door skins S1, S2 covering thecore C varies.

The double press 64 may also be capable of rapid closure. For example,an upper die 70 and a lower die 74 in each of the upper and lowerpresses 62 a, 62 b of the double press 62 may be capable oftransitioning from an open position to contacting the door skins S1, S2and reaching a final pressure in less than 10 seconds. In variousexemplary embodiments, the double press 62 is capable of reaching finalpressure in approximately one second or less. A fast closing doublepress 62 allows for a faster acting adhesive to be used and thereforequicker set and cure times.

In various exemplary embodiments, one of the upper and lower dies 70, 74or both dies 70, 74 may be moved towards and away from the assembleddoor to close the press. As best shown in FIG. 4, actuators 64, such ashydraulic or pneumatic cylinders may be connected to the upper die 70.FIG. 4 depicts the upper press 62 a in an open position and the lowerpress 62 b in a closed position. Each upper and lower press 62 a, 62 bmay also include a conveyor 65, for example a belt conveyor or poweredrollers, to assists in loading and discharging the assembled door fromthe respective press 62 a, 62 b. In an exemplary embodiment, at leastpart of the conveyor 65 is arranged to position the bottom door skin S2above a stationary lower die 74. As best shown in FIG. 4, the lower die74 may be located between the top part of the conveyor 65 and thebottom, or return, part of the conveyor 65. During the pressingoperation, the upper die 70 closes, pressing the door assembly againstthe conveyor 65 and the lower die 74. The conveyor 65 should be madefrom a flexible material that is durable enough to withstand thepressure applied by the dies 70, 74. In various exemplary embodiments,the conveyor 65 may include a first side and a second side with an opencenter section (not shown). The first and second side may include beltsor rollers and be positioned along the edges of the door to contact thedoor skins S1, S2 adjacent the frame F. The first and second sideconveyors and open center section allow the lower die 74 to contact thecentral region of the bottom door skin S2 directly. Various otherdevices and methods for positioning the assembled doors D2 into theupper and lower presses 62 a, 62 b, for example a push rod, may also beused. The press 62 may also include various stops, limits, tactilesensors, and non-tactile sensors may be used to align and position thedoor to square the frame F before pressing.

Although the exemplary embodiments discussed above are with respect to adouble press 62, it should be understood that the pressing apparatus mayalternatively have three, four, five, or more presses. As the number ofpresses increases, the pressing time per press can likewise increasewithout slowing the overall movement time. Moreover, the presses 62 a,62 b may be placed side-by-side on the same level or otherwise orientedas opposed to the stacked relationship shown in FIG. 1. Various materialhandling devices, such as a switching conveyor, may provide theassembled doors to the presses 62 a, 62 b in an alternating fashion.

As shown in FIGS. 5A-5C, in various exemplary embodiments both the upperand lower presses 62 a, 62 b of the double press 62 include an upper die70 having a convex portion 72 a and a lower die 74 having a convexportion 72 b. The convex portions 72 a, 72 b over compress at least thecentral portions of the top and bottom door skins S1, S2 so that atleast part of the interior surface of the door skins S1, S2 is coplanarwith or below the respective surface of the frame F to which the skin isattached. The over compression helps increase the bond between the doorskins S1, S2 and the core C. In various exemplary embodiments, theradius of curvature of the convex portions 72 a, 72 b is between about0.1 mm and about 2 mm. In certain embodiments the radius of curvature ofthe convex portions 72 a, 72 b is between about 0.2 mm and approximately0.5 mm. The radius of curvature of the convex portions 72 a, 72 b mayvary however, depending on design and production characteristics such asthe design of the door, the size of the door, the press time, and theamount of pressure applied.

FIGS. 5A-5C depict an exemplary embodiment where the convex portions 72a, 72 b begin approximately at the outer edges of the upper and lowerdies 70, 74. In an exemplary embodiment shown in FIG. 6, a flat section75 a, 75 b extends around the outer edge of the dies 70, 74, and theconvex portions 72 a, 72 b begin in a more centrally located region. Theflat sections 75 a, 75 b may have approximately the width of typicalstiles on the longitudinal sides and the width of typical rails on thelateral sides. The flat section 75 a, 75 b may also be slightly largerthan a standard frame F size to accommodate different width doors, asthe size of the convex sections 72 a, 72 b may be varied and stillobtain desirable results. For example, relatively small central convexsections 72 a, 72 b compared to the length and width of a standard doormay be provided in the upper and lower dies 70, 74 which could stilleffectively reverse the natural bowing of the door skins S1, S2 andtherefore help prevent pillowing and delamination.

As best shown in FIG. 5A, when the door is placed into the press astrong adhesive connection may be present between the perimeters of thedoor skins S1, S2 and the stiles 2 and rails 6, but internal stresses inthe door skins S1, S2 may lead to pillowing and separation from the coreC. The pillowing effect can cause separation between the door skins S1,S2 and the core C of as much as 1 inch or greater, and can reach about 2inches at the very center of the door skins S1, S2. As shown in FIG. 5B,when the press is closed, the convex portions 72 a, 72 b over compressthe central portion of the door skins S1, S2 respectively. The overcompression not only helps to bond the door skins S1, S2 to the core C,but also redirects the natural bowing of the door skins S1, S2. Becausethe door skins S1, S2 are fixed at the frame F, the internal forces havea tendency to push away from the frame F, forcing the door skins S1, S2away from the core C. Once the bowing is reversed, any internal stressesremaining in the door skins S1, S2 are redirected inwards, pushing thecenter of the door skins S1, S2 towards the core C as opposed to awayfrom it. As shown in FIG. 5C, when the press is opened, the pillowing iseliminated and the door skins S1, S2 may return to an approximately flatshape. The resultant door has increased bond strength compared totypical doors with less chance of pillowing or delamination.

In various exemplary embodiments, the door skins S1, S2 may have aslight concave cross-sectional shape after pressing is complete. FIG. 7Ashows a pressed door D2 and FIGS. 7B and 7C depict cross-sectional viewsof FIG. 7A showing the concave shape imparted to the door D2. It shouldbe noted that the concave sectional profile shown in FIGS. 7B and 7C maynot be to scale. The concave shape retained in the door skins S1, S2after pressing is completed is due to the fact that the door skins S1,S2 may undergo plastic deformation resulting from the over compressionand therefore may not return to a completely planar surface immediatelyfollowing the pressing operation. However, over time, such as after thestacked doors are removed from the presses and stacked, the door skinsS1, S2 may further revert partly or completely toward or to their planarsurfaces. The concave shape may be less than noticeable to the unaidedhuman eye and therefore undetectable to consumers. For example, theresulting shape of the door skins S1, S2 may have a maximum concavedepth that is less than the maximum convex height of the upper and lowerdies 70, 74. In various exemplary embodiments, the maximum depth of theconcave section, when present, is about 0.05 mm to about 0.5 mm.

FIGS. 5A-5C depict an exemplary embodiment where the convex portions 72a, 72 b are formed integrally with the upper and lower dies 70, 74. Invarious other exemplary embodiments an upper spacer 76 a and a lowerspacer 76 b are inserted between the upper and lower dies 70, 74 and thedoor skins S1, S2 respectively as shown in FIG. 8. The spacers 76 a, 76b may be made from a rigid material, for example a metallic material, orthey may be made from a resilient material such as a silicone, polymer,elastomer, wood, or cardboard. The spacers 76 a, 76 b may have a convexshape similar to the dies 70, 74 shown in FIGS. 5A-5C, or they maysimply provide a raised area to over compress the door skins S1, S2. Theuse of spacers 76 a, 76 b allows different sizes, shapes, and amounts ofcontour to be interchanged for different door sizes and designs. A humanoperator or robotic handling device may place the spacers 76 a, 76 bbetween the door skins S1, S2 and the upper and lower dies 70, 74 as theassembled door is loaded into the double press 62. The spacers 76 a, 76b may also be placed either above or below the top belt of the conveyor65 when used in conjunction with the exemplary embodiment depicted inFIG. 4. The handling device may determine the type of spacers 76 a, 76 bappropriate for the door based on information received from an operator,a central computing system, through image recognition, or various othertechniques associated with variable batch production.

In various other exemplary embodiments, the convex or raised portion isachieved through an upper plate 78 a and a lower plate 78 b that areattached to the upper and lower dies 70, 74 as shown in FIG. 9. Theupper and lower plates 78 a, 78 b may be made from various materialsincluding elastomeric, metallic, ceramic, cellulosic, or compositematerials. Multiple upper and lower plates 78 a, 78 b may be used, eachhaving a different size, shape, and/or radius of curvature. Thedifferent upper and lower plates 78 a, 78 b may be used in associationwith different door sizes and designs. The upper and lower plates 78 a,78 b may be removably connected to the upper and lower dies 70, 74. Forexample, the plates 78 a, 78 b may be attached to the upper and lowerdies 70, 74 through removable mechanical fasteners such as bolts orlatches, or through a magnetic connection. Different upper and lowerplates 78 a, 78 b may be interchanged manually or automatically asdiscussed above in relation to the upper and lower spacers 76 a, 76 b.

In various exemplary embodiments, the over compression of the door skinsS1, S2 is achieved through an upper membrane 80 a and a lower membrane80 b fastened to the upper and lower dies 70, 74 as shown in FIG. 10.The membranes 80 a, 80 b may have a thickness of about 0.1 mm to about2.0 mm. The membrane may be made from a material that allowsdifferential compression, such as a material comprising silicone orrubber. When pressed onto the door skins S1, S2, the compression of theupper and lower membranes 80 a, 80 b is greatest at the areas adjacentthe rails and stiles 82 and decreases towards the center of the door 84.Therefore the upper and lower membranes 80 a, 80 b are thicker at thecenter of the door skins S1, S2 and cause over compression. The variablecompression allows a single set of upper and lower membranes 80 a, 80 bto press different door sizes and designs. Accordingly, the upper andlower membranes 80 a, 80 b may be permanently attached to the upper andlower dies 70, 74 or they may be semi-permanently attached where asecure constant connection is desired but replacement upper and lowermembranes may be provided. In various embodiments, however, the upperand lower membranes 80 a, 80 b may be removably secured to the upper andlower dies 70, 74 so that membranes 80 a, 80 b of different sizes,shapes, materials, or any combination thereof may be easilyinterchanged.

In an effort to reduce or eliminate any markings in the surface of doorscaused by the raised surfaces created by the upper and lower dies 70,74, a further alternate embodiment to the present invention providesupper and lower membranes or wear resistant belts that substantiallycover the entire platen surface including the surface of the upper andlower dies 70, 74 to prevent the hardened steel from marring the doorsthat are acted upon by the platen during the pressing process. The wearresistant belt is preferably formed with an internal rubber core of highdurometer with an outer coating of a relatively softer material that isresistant to wear during the pressing process. Thus, the upper and lowermembranes or wear resistant belts 198 define expandable, compressiblemembers on top of the upper and lower dies 70, 74. An example of awear-resistant belt is disclosed in U.S. Pat. No. 9,314,983, thecomplete disclosure of which is incorporated herein by reference.

In various exemplary embodiments, the convex or raised portion isachieved through an upper expandable membrane 86 a and a lowerexpandable membrane 86 b attached to the upper and lower dies 70, 74 asshown in FIG. 11. The expandable membranes 86 a, 86 b are made of anexpandable or otherwise flexible material. Gas, such as compressed air,is supplied to upper and lower chambers 88 a, 88 b formed between theupper and lower dies 70, 74 and the upper and lower expandable membranes86 a, 86 b respectively. The added pressure from the gas is transferredto the door skins S1, S2 and causes over compression during pressing.Though only a single chamber 88 a, 88 b is shown in FIG. 11 associatedwith each die 70, 74, there may be more than one chamber and thechambers may be selectively supplied with gas to provide differentamounts of compression to different door sections or to different doorsizes and designs.

FIGS. 12-14 illustrate an alternative embodiment for the platens wherebythe over compression of the door skins S1, S2 is achieved through shims180, 190, 192, 194-196 provided on the upper and lower dies 70, 74 asshown in FIG. 10. The shims 180, 190, 192, 194-196 may have a thicknessof about 0.1 mm to about 2.0 mm. The shims 180 are preferably made fromhardened steel, but also may be made from a material that allowsdifferential compression, such as a material comprising silicone orrubber. When pressed onto the door skins S1, S2, the compression of theshims is greatest at the center of the door 84 and decreases toward theareas adjacent the rails and stiles 82. Therefore, the shims define asurface that is thicker at the center of the door skins S1, S2 and causeover-compression. Shims of different width and height are employed toaccommodate door skins of different sizes. In the preferred embodiment,the shims have a perimeter that terminates at about 4 (four) inches fromthe perimeter of the door skin.

The central shim 180 may be permanently attached to the upper and lowerdies 70, 74 via fasteners 180′ or they may be semi-permanently attachedwhere a secure constant connection is desired but replacement upper andlower membranes may be provided. In various embodiments, however, theshims 180 may be removably secured to the upper and lower dies 70, 74 sothat shims 180 of different sizes, shapes, materials, or any combinationthereof may be easily interchanged.

In the preferred embodiment, the central shim 180 is permanentlyattached to the upper and lower dies 70, 74 via fasteners, andperipheral shims 190, 192, 194-196 are hydraulically driven to be raisedand lowered with respect to the central shim 180 to accommodate doors ofdifferent sizes. The peripheral shims 190, 192 are driven by hydraulicpressure delivered via hydraulic ports ‘hp’ to the hydraulic chambers‘hc’. FIG. 13 illustrates various hydraulic connectors at the hydraulicports ‘hp’ whereby hydraulic pressure is delivered to the hydraulicchambers in a controlled manner as would be understood by those of skillin the art.

Turning to FIGS. 14A-14C, the platen 70, 74 is illustrated with theperipheral shims 190, 192 in various positions with respect to centralshim 180. FIG. 14A illustrates a first shim position for doors ofsmaller size, e.g., 24″, whereby the peripheral shims 190, 192 arerecessed into the platen 70, 74. FIG. 14B illustrates a second shimposition for doors of intermediate size, e.g. 30″, whereby theperipheral shims 190 are raised to be substantially flush with thecentral shim 180 while the peripheral shims 192 remain recessed into theplaten 70, 74. FIG. 14C illustrates a third shim position for doors oflarger size, e.g. 36″, whereby all the peripheral shims 190, 192 areraised to be substantially flush with the central shim 180. It is notedthat the lateral shims 194-196 are likewise raised and lowered byhydraulic pressure depending on the size of the door being acted upon bythe platen 70, 74.

In an effort to reduce or eliminate any markings in the surface of doorscaused by the raised surfaces created by the shims 180, 190, 192,194-196, the present invention provides a wear resistant belt, shown aselement 198 in FIG. 14C, that substantially covers the entire platensurface including the shims to prevent the hardened steel from marringthe doors that are acted upon by the platen during the pressing process.The wear resistant belt is preferably formed with an internal rubbercore of high durometer with an outer coating of a relatively softermaterial that is resistant to water during the pressing process.

As best shown in FIG. 1, after the pressing station 62, the assembleddoor D2 is taken off the main production line 1. The door D2 then maypass through a number of optional finishing operations as needed. Forexample, the door may be passed through a stile trimming station 90 anda rail trimming station 92 to remove excess material. If the blades ofthe trimming stations 90, 92 are parallel the door may need to berotated between the stile trimming station 90 and the rail trimmingstation 92. After the edges have been trimmed, the door may be placedthrough an edge coating station 94. Here the edges of the door, such asthe exposed rails 6 a, 6 b and stiles 2 are coated or painted. Otherpainting or coating may be accomplished at this station or separately.

When the door D2 is completed, it passes to an inspector 96 who checksthe door for quality issues. In various exemplary embodiments thequality inspection may be performed automatically as discussed abovewith respect to the door skin assembly station 40. Any unacceptable dooris either discarded or reworked, and all doors passing inspection aresent to palletizer 98 for stacking.

A number of commonly used and commercially available adhesives have beendiscussed above such as PUR and EVA hot melt adhesives. However, aspectsof the present invention are also directed to the novel use of adhesivecompositions. In an exemplary embodiment, a PUR adhesive comprisingpolyurethane and isocyanurate is used in the above-disclosed system.These chemicals increase the initial green or set strength of theadhesives, securing the bond between the door skin and the frame,eliminating delamination caused by the stresses of bowed or warpedskins.

The foregoing detailed description of the certain exemplary embodimentshas been provided for the purpose of explaining the principles of theinvention and its practical application, thereby enabling others skilledin the art to understand the invention for various embodiments and withvarious modifications as are suited to the particular use contemplated.This description is not necessarily intended to be exhaustive or tolimit the invention to the precise embodiments disclosed. Additionalembodiments are possible and are intended to be encompassed within thisspecification and the scope of the appended claims. The specificationdescribes specific examples to accomplish a more general goal that maybe accomplished in another way.

What is claimed is:
 1. A door press for pressing door assemblies,comprising: a first die comprising a first fixed surface; a first fixedshim having a first shim surface raised from the first fixed surface;and a plurality of first movable shims, each first movable shim having afirst movable shim surface, each of the first movable shims beingmovably connected to the first die to move between a raised position inwhich the first movable shim surface is substantially flush with thefirst shim surface and a lowered position in which the first movableshim surface is substantially flush with the first fixed surface,wherein the first shim surface is rectangular in shape and has a lengthand a width, the first movable shims comprise a first set of shimswhich, when in the raised position, extend the length of the first shimsurface, and a second set of shims which, when in the raised position,extend the width of the first shim surface.
 2. The door press of claim1, further comprising a wear resistant belt covering the first fixedsurface, the first fixed shim, and the first movable shims.
 3. The doorpress of claim 1, further comprising hydraulically operable assembliesoperably associated with the first movable shims for moving theplurality of first movable shims.
 4. The door press of claim 1, whereineach of the first movable shims is independently movable.
 5. The doorpress of claim 1, further comprising a second die juxtaposed to thefirst die and comprising a second fixed surface facing the first fixedsurface.
 6. The door press of claim 5, further comprising a second fixedshim having a second shim surface raised from the second fixed surface;and a plurality of second movable shims, each of which has a secondmovable shim surface, each of the second movable shims being movablyconnected to the second die to move between a raised position in whichthe second movable shim surface is substantially flush with the secondshim surface and a lowered position in which the second movable shimsurface is substantially flush with the first fixed surface.
 7. The doorpress of claim 6, further comprising hydraulically operable assembliesoperably associated with the second movable shims for moving the secondmovable shims.
 8. The door press of claim 6, further comprising a wearresistant belt covering the second fixed surface, the second fixed shim,and the second movable shims.
 9. The door press of claim 6, wherein thesecond shim surface is rectangular in shape and has a length and awidth, the second movable shims comprise a first set of shims which,when in the raised position, extends the length of the second shimsurface, and a second set of shims which, when in the raised position,extends the width of the second shim surface.
 10. The door press ofclaim 6, wherein each of the first movable shims are independentlymovable, and the second movable shims are independently movable.
 11. Adoor-making system, comprising: a) an adhesive coating station forapplying adhesive to at least one of a door frame having opposite firstand second surfaces, a first door skin, and a second door skin; b) anassembly station for joining the first and second door skins to theopposite first and second surfaces of the door frame, respectively, toform an assembled door; c) a door press comprising: i) a first diecomprising a first fixed surface, ii) a first fixed shim having a firstshim surface raised from the first fixed surface, and iii) a pluralityof first movable shims, each of which has a first movable shim surface,each of the first movable shims being movably connected to the first dieto move between a raised position in which the first movable shimsurface is substantially flush with the first shim surface and a loweredposition in which the first movable shim surface is substantially flushwith the first fixed surface; and d) a material handling device fortransporting the assembled doors to and from the door press.
 12. Thedoor-making system of 11, wherein the door press further comprising asecond die comprising a second fixed surface facing the first fixedsurface.
 13. The door-making system of 12, wherein the door pressfurther comprising a second fixed shim having a second shim surfaceraised from the second fixed surface; and a plurality of second movableshims, each of which has a second movable shim surface, each of thesecond movable shim being movably connected to the second die to movebetween a raised position in which the second movable shim surface issubstantially flush with the second shim surface and a lowered positionin which the second movable shim surface is substantially flush with thefirst fixed surface.
 14. The door-making system of 13, wherein thesecond shim surface is rectangular in shape and has a length and awidth, the plurality of second movable shims comprises a first set ofshims which, when in the raised position, extend the length of thesecond shim surface, and a second set of shims which, when in the raisedposition, extends the width of the second shim surface.
 15. Thedoor-making system of 11, wherein the first shim surface is rectangularin shape and has a length and a width, the first movable shims comprisea first set of shims which, when in the raised position, extend thelength of the first shim surface, and a second set of shims which, whenin the raised position, extend the width of the first shim surface. 16.The door-making system of 11, further comprising a wear resistant beltcovering the first fixed surface, the first fixed shim, and the firstmovable shims.
 17. The door-making system of 11, further comprisinghydraulically operable assemblies operably associated with the firstmovable shims for moving the plurality of first movable shims.
 18. Thedoor-making system of 11, wherein each of the first movable shims areindependently movable.
 19. A method of pressing a door assembly,comprising: a) providing a door press comprising i) a first diecomprising a first fixed surface, ii) a first fixed shim having a firstshim surface raised from the first fixed surface, and iii) a pluralityof first movable shims, each of which having a first movable shimsurface, each of the first movable shims being movably connected to thefirst die to move between a raised position in which the first movableshim surface is substantially flush with the first shim surface and alowered position in which the first movable shim surface issubstantially flush with the first fixed surface; b) selectivelyadjusting the orientation of each of the first movable shims so that acombined area of the first shim surface and the first movable shimsurfaces corresponds to a center area of a face of the door assembly; c)positioning a door assembly in the press; and d) pressing the doorassembly in the press.
 20. The method of claim 19, wherein step b)comprises orienting each of the first movable shims in one of the raisedposition or the lower position, so that the first shim surface and thefirst movable shim surfaces in the raised position collectively form asurface area with a perimeter that is inwardly of a perimeter of theface of the door assembly.